218 l.V.V l/.N .V/;U' YORK ACADEMY OF SCIENCES 



world, at all events, they did not reappear after the early Comanchcan. 

 A dinosaur fauna largely similar to that of the Jurassic in habits and 

 adaptaticjn in other respects, developed during the late Cretaceous in 

 the North. It contains no Sauropoda, but it includes amphibious types 

 (Traehodontidae) with marked aquatic adaptation, gigantic terrestrial 

 swamp and forest dwellers, like the ceratopsians, tyrannosaurs and anky- 

 losaurs, and many smaller more agile forms. These Cretaceous giants, 

 however, appear to have evolved, not from amphibious or aquatic dino- 

 saurs of the Jura, but, in part at least, from small and little known forms, 

 of more upland adaptation, which had been much more highly specialized 

 for dry-land life than any of the Jurassic swamp dwellers, and had re- 

 adapted themselves to the forest and swamp environment of the later 

 Cretaceous. The trachodonts and ceratopsians, for instance, while re- 

 lated to the earlier iguanodonts, cannot be directly derived from them 

 but must be traced back to some unknown contemporary which was highly 

 progressive in developing efficient grinding dentition, compact feet with 

 flattened hoofs, etc. — characters which in a survey of mammalian adapta- 

 tion we find to be especially associated with upland habitat. The evi- 

 dences of former dry-land adaptation are not so clearly shown in the 

 other swamp-giants of the late Cretaceous, but they may perhaps be 

 shown by further study. ^*'^ 



In sum, we may find in the hypothesis of recurrent climatic change, 

 and in the primary adaptation of the dinosaurs as a dry-land adaptation 

 of Eeptilia and their secondary readaptations to forest and swamp life, 

 a fairly satisfactory solution of their distribution and phylogeny. Lull, 

 in his able discussion of the subject (1910), explains their adaptation 

 along these lines. But at present our data, both of correlation and 

 identification, are too uncertain to allow of positive and detailed con- 

 clusions in regard to the centers of dispersal and course of migration of 

 the dinosaurs. That the sauropods survived in the southern continents 

 long after their extinction in the north appears proven, if we accept the 

 stated geological correlations of the southern formations where they are 

 found and set aside as an erroneous identification the reported occurrence 

 of a sauropod in the Dan Ian of France. ^°' That the Theropoda survived 

 into the Eocene in South America and Theropoda and Predentata into 

 the Paleocene in North America is not improbable on a priori grounds, 



1*1 L. DoLLO (Bull. Soc. Belg. G60I., xix, p. 441. 1905) has shown that the quadrupedal 

 gait of many of the Predenlate dinosaurs is a secondary adaptation from hipedal ances- 

 try. I believe this to be true, to a less extent, of the Sauropoda as well. 



"2 p. NopscA (Rep. Geol. Mag., vol. vii, p. 261. 1910) states that the femur on 

 which this recorded occurrence is based is not a sauropod but a trachodont dinosaur, 

 allied to or identical with Telmatosaurus of the Gosau beds of Austria. 



